α-和γ-环糊精改性法制备的Ni/SBA-15催化剂的物化性质及其在甲烷二氧化碳重整中的催化性能

以多羟基有机物α-或γ-环糊精为分散促进剂制备了Ni/SBA-15催化剂，通过N2吸附-脱附、X射线衍射、透射电镜、程序升温还原和热重等手段对该催化剂的物理化学性质进行了表征，并将其应用于甲烷二氧化碳重整(CRM)制合成气反应。结果显示，与采用传统浸渍法制备的Ni/SBA-15催化剂相比，采用α-或γ-环糊精改性法制备的催化剂具有更小的NiO颗粒，并在CRM中显示出更高的催化活性及更强的抗积碳性能。机理研究表明，采用传统浸渍法制备Ni/SBA-15催化剂时，浸渍液中的Ni2+主要在浓度梯度的作用下逐渐进入到SBA-15孔道内部， Ni2+水合物容易团聚，分散程度较低；而采用α-或γ-环糊精改性方法制备催化剂时，在水溶液中Ni2+与环糊精形成包覆物，环糊精携带Ni2+进入SBA-15孔道内，并且环糊精的存在使得Ni2+之间相互隔离，以高度分散形态存在于SBA-15孔道表面，有利于后续热处理中NiO在载体上较好地分散。

Effects ofα-andγ-cyclodextrin-modified impregnation method on physicochemical properties of Ni/SBA-15 and its catalytic performance in CO2 reforming of methane

Organic compounds containing multiple hydroxyl groups, namely α‐cyclodextrin and γ‐cyclode‐xtrin, were used as additives for promoting Ni dispersion on supported Ni/SBA‐15 catalysts. Cata‐lysts prepared using modified and unmodified impregnation methods were characterized using N2 adsorption‐desorption isotherms, X‐ray diffraction, transmission electron microscopy, tempe‐rature‐programmed reduction, and thermogravimetric analysis, and their catalytic performance in the CO2 reforming of methane (CRM) to syngas was evaluated. The results show that compared with Ni/SBA‐15 prepared using a conventional impregnation method, the cyclodextrin‐modified cata‐lysts had smaller NiO particles. They also exhibited higher catalytic activity and had stronger ability to resist carbon deposition in the CRM. Mechanistic studies showed that for the unmodified cata‐lysts, Ni2+could migrate into the channels of SBA‐15 as a result of concentration differences, and the Ni species were sintered during the following thermal treatment processes, and could not be well dispersed. In contrast, various types of complex were formed between Ni(NO3)2 and the cyclodex‐trins, and this would be favorable for Ni2+being taken into the channels of the SBA‐15. The presence of cyclodextrins was beneficial to the mutual isolation of Ni species, and finally resulted in better dispersion of Ni species.